Parse the Message Inbound For Emojis

/**
 * Parse the Message Inbound For Emojis
 *
 * @param string $txt
 * The received message, where to find the Emojis.
 *
 * @param boolean $span
 * If "true", the function will return an html tag
 * Example: <span class="emoji" id="emoji-1F604"></span>
 * this will show the smiling face, require emojisprite.css and emojisprite.png
 *
 * Otherwise, if it is "false", return an id. Example, ##1F604##.
 *
 * @return string
 */